Laser processes for thin film structures and devices such as thin film batteries (TFBs), electrochromic (EC) devices, solar cells, etc. are used to selectively ablate/scribe various layers from the front side (thin film side) of the substrate, leaving certain layers intact and undamaged. For selective laser ablation/scribing of semiconductors/dielectrics from metals, heat easily transfers from semiconductors/dielectrics to underlying metals due to the high thermal diffusivity of metals. See FIG. 1 which is an illustration of the estimated extent of the heat zone 105 in which laser ablation damage by a stationary laser beam 101 may occur—the heat zone penetrates the metal layer 103 and even extends into the substrate/underlying layer 104; estimated isotherms 106 are shown within the heat zone 105—the isotherms are not calculated or measured, but are estimated based on the observed extent of laser damage. Moreover, part of the laser light may penetrate through the semiconductors/dielectrics 102 and enter into the metals 103, which can be absorbed by the metals and then further increase the temperature of the metals. The temperature of underlying metals can reach up to their vaporization point during laser ablation of semiconductors/dielectrics, which may lead to melting and vaporization of the underlying metals, and result in functional impairment of the thin film devices. For example, in TFB processing it may be desirable to remove, using laser ablation from the front side, dielectric layers from over conductive current collector layers to allow for formation of bonding pads. See FIG. 2 which illustrates a typical thin film battery (TFB) stack, including a substrate 201, a cathode current collector (CCC) 202, a cathode (e.g., LiCoO2) 203, an electrolyte (e.g., LiPON) 204, an anode (e.g., Li, Si—Li and other intercalated oxides) 205, an anode current collector (ACC) and a protective coating 207. However, during laser direct patterning of TFBs, the current collector layer (usually less than 1 micron of Ti/Au) may reach high temperatures of up to their vaporization point when the electrolyte (LiPON, e.g.) and cathode (LiCoO2, e.g.) are being removed by laser ablation. This high temperature causes the current collector to melt or even vaporize, and inevitably reduces current collection efficiency and overall TFB charging/discharging efficiency.
Clearly, there is a need for improved approaches to laser direct patterning of TFB, EC and similar structures and devices that does not impair the function of the remaining layers of the thin film structures and devices.